A company is consuming parts in the manufacturing of other products. Each of…
2021
A company is consuming parts in the manufacturing of other products. Each of the part is either manufactured within the company or purchased from the external suppliers or both. For each part, partnumber, partname is maintained. Attribute batchnumber is maintained if the consumed part is manufactured in the company. If part is purchased from external supplier, then supplier name is maintained. Which of the following constraints need to be considered when modelling class/subclass concepts in ERD for the given problem.
- A.
Total specialization and overlapping constraints
- B.
Disjoint constraint only
- C.
Partial participation
- D.
Partial participation and disjoint constraints
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Correct answer: A
Answer: Total specialization and overlapping constraints.
Why total specialization: Every part must be manufactured, purchased, or both, so each Part must belong to at least one subclass (manufactured or purchased).
Why overlapping: The phrase "or both" allows a part to be in both subclasses simultaneously, so subclasses are overlapping (not disjoint).
Subclass attributes: batchnumber is an attribute of the manufactured subclass; supplier name is an attribute of the purchased subclass.
ERD modeling recommendation: Model a supertype Part with two subclasses named e.g. ManufacturedPart and PurchasedPart. Indicate total specialization (every Part belongs to at least one subclass) and mark the specialization as overlapping. Attach batchnumber to ManufacturedPart and supplier name to PurchasedPart.
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